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Nuclear Event – Automatic Reactor Trip (Fire): Watts Bar Nuclear Plant, Unit 2

2016/08/31

North America – USA | State of Tennessee, Rhea County, Spring City, Watts Bar Nuclear Plant
Location: 35°36’10.0″N 84°47’22.0″W
Site Operational Age: ~31 years
Event: UNUSUAL EVENT/AUTOMATIC REACTOR TRIP/FIRE

Nuclear Event in USA on Tuesday, 30 August, 2016 at 21:20 [EDT].

NOTICE OF UNUSUAL EVENT – FIRE IN A MAIN BANK TRANSFORMER

A fault occurred on the unit 2 “B” main bank transformer resulting in an oil fire. The main turbine tripped resulting in a reactor trip. All control rods fully inserted and no safety or relief valves lifted. Decay heat is being removed via steam dumps to the main condenser and feeding steam generators with auxiliary feedwater. Electrical power is through the normal shutdown electrical lineup.

Offsite assistance was requested from the county and off duty fire brigade members.

At 2228, the fire was reported as out. Spray is continuing and a reflash watch is being set.

Unit 1 continued to operate at 100% power throughout the event.

Notified the DHS SWO, FEMA Ops Center, DHS NICC, FEMA National Watch Center (E-mail) and Nuclear SSA (E-mail).

* * * UPDATE AT 2352 EDT ON 08/30/2016 FROM MICHAEL BOTTORFF TO JEFF HERRERA * * *

“On August 30, 2016, at 2110 EDT, Watts Bar Nuclear Plant Unit 2 reactor tripped due to an electrical fault affecting the 2B Main Bank Transformer, resulting in a fire in the transformer.

“Concurrent with the reactor trip, the Auxiliary Feedwater system actuated as designed.

“All Control and Shutdown rods fully inserted. All safety systems responded as designed. The unit is currently stable in Mode 3, with decay heat removal via Auxiliary Feedwater and main steam dump systems. Unit 2 is in a normal shutdown electrical alignment.

“The fire was out at 2230 EDT. The cause of the fire is currently under investigation.

“The fire was reported at 2149 EDT. Local Fire Departments responded to the site as requested.

“The reactor trip and system actuation is being reported under 10CFR50.72(b)(3)(iv)(A) and 10CFR50.72 (b)(2)(iv)(B).

“There was no effect on WBN Unit 1.

“The NOUE was exited at 2342.

“The NRC Senior Resident Inspector has been notified.”

The Licensee notified the State of Tennessee.

Notified the R2DO (Bartley), IRD MOC (Stapleton), NRR EO (Miller), DHS SWO, FEMA Ops Center, DHS NICC, FEMA National Watch Center (E-mail) and Nuclear SSA (E-mail).

Source: NRC  Event Number: 52210

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Previous Events

Nuclear Event in USA on Tuesday, 23 August, 2016 at 13:56 [EDT]. MANUAL TRIP DUE TO A LOSS OF MAIN FEEDWATER

Nuclear Event in USA on Monday, 20 June, 2016 at 15:40 [EDT]. RPS ACTUATION – CRITICAL/AUTOMATIC REACTOR TRIP

Nuclear Event in USA on Sunday, 05 June, 2016 at 12:27 [EDT]. REACTOR TRIP AND ECCS ACTUATION CAUSED BY TURBINE GOVERNOR VALVE FAILURE

Nuclear Event in USA on Tuesday, 22 March, 2016 at 11:31 [EDT]. WATTS BAR AUTOMATIC REACTOR TRIP UNIT 1 [due to the actuation of the Over Temperature Delta Temperature bistables.]

Nuclear Event in USA on Thursday, 17 March, 2016 at 01:15 [EDT]. LOSS OF EMERGENCY AND AUXILIARY GAS TREATMENT SYSTEMS – UNIT 1

Nuclear Event in USA on Wednesday, 09 March, 2016 at 03:42 [EST]. UNUSUAL EVENT DECLARED DUE TO A FIRE GREATER THAN 15 MINUTES – UNIT 2


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